超声成象测井仪声波换能器的特性分析

Property Analysis of Disc Transducer for Ultrasonic Imaging Logging Tool,

厚度方向极化的圆片状压电换能器已经广泛地被用到声波成象测井仪和 CET水泥胶结质量评价仪上。人们仅仅考虑了传播媒质对接收的声波信号的影响 ,而很少考虑声源对接收的声波信号的影响。文中分析了这种换能器的瞬态响应 ,建立了它的等效电路 ,推导出声波函数 ,并指出换能器在三种发射模式 :过阻尼、临界阻尼和振荡模式。只有振荡模式具有实际用途。换能器的发射模式由换能器的材料特性、周围耦合液体的机械负载和驱动电路的输出阻抗等因素决定。通过改变这些参数 。

A thin disc transducer polarized in thickness direction is widely used in ultrasonic imaging logging tool and CET logging tool.Many published literatures on coustic logging concentrated on propagation phenomena of the acoustic wave in the borehole and in the formation,with no account of the excitation of the source and the coupling with the surrounding medium.The transient response is analysed.Its equivalent circuit is set up and its source function is derived.There are three transmitting modes for the transducer:over damped,critical damped and oscillatory modes.Only the oscillatory is practical application.The transmitting mode of the transducer is determined by the material property of the transducer,the machanical load of the surrounding coupling medium and the output impedance of the driving circuit.By changing these factors,the quality of the transmitted acoustic wave signal and acoustic imaging can be improved.